Casting apparatus compensating for shrinkage of the cast material



APF 13, 194.8' IP. CAMPBELL Er AL 2,439,450

CASTING APPARATUS COIIPEHSATING FOR SHRINKAGB 0F THE CAST IATERIAL Filed April 14.1945 2 sheets-sheet 2 e Y Z2 25 'fz/f Patented Apr, 13, 1948 UNITED ",s'rA'rEs PATENT oFFiE n CASTING APPARATUS COMPESATING FOR SHRINKAGE F THE CAST MATERIAL rhimp campbell, Whittier, ana william n. Maxwell, Newport Beach, Calif.

`Application April 14, 1943, Serial No. 482,990

14 claims. (olaz-1) This invention relates to the production of articles by molding and casting` operations and relates more particularly to apparatus useful in carrying on such operations. of this invention is to provide dependable and very effective apparatus useful in molding and casting operations.

The apparatus of the invention is`useful in various casting or forming operations where it is desirable or necessary to impose pressure on the material being cast or formed. 'I'he invention is not connected with the forming or casting of any given materiel or of any given class of materials or for use with any given process of molding, casting or forming of materials. We will herein refer to th'e invention as employed in connection with the casting of metals such as iron, steel, brass, aluminum, etc., it being understood that this is merely for the purpose of explanation and is not to be considered as limiting either the scope or lapplication of the invention,

It has long been recognized that in order to produce sound castings provision must be made to compensate for or to feed the volumetric shrinkage which accompanies the solidification of the material in the mold. Heretofore, in ordinary molding operations, large reservoirs or heads of molten material were arranged in communicationwith the mold cavity to supply the deflciency resulting from the volumetric shrinkage. Such heads require the pouring of a large excess of material and are often difficult to properly locate in the mold. Further, such' heads do not actually feed material to the mold but rather form a reservoir from which material is drawn A general object molten material in the mold cavity. The pressure units of the invention may be arranged or entered in relatively small cavities of the mold which have communication with the mold cavity so as to be contacted by the molten material. The units are energized by the h'eat of the molten material so they increase in volume and exert pressure to feed molten material into the mold cavity and thus compensate for or feed the volumetric shrinkage accompanying the solidifying of the molten material in the mold cavity. The invention thus insures the production of` sound, dense castings having a minimum of internal stress.

Another object of this invention is to provide an apparatus of the character referred to in which the pressure units are very simple and inexpensive and are such that they maybe easily set in the mold'as it is being made up or may be inserted into working position after the metal has been poured.

The various objects and features of our invention will be fully understood from the following detailed description of typical lpreferred forms of th'e apparatus and typical manners of using the apparatus of the invention, throughoutwhich description reference is made to the acas the shrinkage occurs.` The use of such heads A adds materially to the cost of casting and is not always productive of good results.

An object of this invention is ,to provide a simple, practical and very inexpensive means for feeding or compensating for the volumetric shrinkage accompanying the solidication of the molten metal in the mold cavity, which means eliminates the necessity of the large heads heretofore employed.

Another object of the invention is to provide a device of the character mentioned-which 'acts to actually feed the material with pressure.

Another object of this invention is to provide apparatus of the characterreferred to embodying one or more pressure producing units energized by the heat of the molten material to expand and thus compensate for the volumetric shrinkage accompanying th'e solidiflcation of the companying drawings, in which:

Fig. 1 is a perspective view of a conventional sand mold showing the mold in section to illustrate a typical application of the invention. Fig.

2 is a detailed sectional view of one form of the invention showing it applied in a typical manner. Fig. 3 is a view similar to Fig. 2 'showing another form of construction. Fig. 4 is a perspective view of a typical casting showing several units in connection therewith as they would appear upon the casting being removed from the mold.; Fig. 5 is a view similar to Fig. 1, showing another adaptation of the invention,

The apparatus is useful in connection with sand molds, plaster molds, carbon molds, permanent die type molds, composition molds and molds employing a combination of materials, and is useful in the casting of various metals, alloys, plastics, etc., and any other material Where heat is employed to melt the material to facilitate forming or creating the finished article. In the following detailed description we will describe the invention as employed in the casting of metal it being understood that this is merely explanatory ,and is not intended as limiting or restricting the be described in connection with the mode of employing the apparatus.

The apparatus of Fig. 1 may be said to comprise, generally, two mold sections I Il and II, having a mold cavity I2 and one or more head cavities I3 and a pressure unit I4 in each head cavity I3.

The character of the mold may be varied greatly depending upon the nature of the material to be cast, the size and character of the article to be formed, and other factors. In the case illustrated the mold comprises the two sections and I I made u`p in typical foundry asks I5. The molds IIJ and I I may be of foundry sand or. as above pointed out may be formed of any selected or required refractory material or permanent mold material. The mold cavity I2 may occur in any portion of the mold, as conditions may require. In the case illustrated the mold cavity I2 is provided in the mold sections III and II at the line of parting I6 and a gate I1 is provided in the upper or cope section III to communicate with the cavity I 2.l

In accordance with the invention a cavity I3 is formed in the mold to communicate with the mold cavity I2. 'I'his cavity I3 may be termed a head although it diers materially from the heads heretofore employed. 'I'he size, shape and location of the cavity I3 depends upon the proportions and shape of the mold cavity I2 and the article to be cast. In the simple illustrative example of Fig. 1 there is a single cavity I3 extending laterally from one side of the mold cavity I2 at or adjacent the line of parting IS. It i-s to be understood that there may be a plurality of the cavities I3 arranged to communicate with those portions of the vmold cavity I2 where thereis likely to be the greatest volumetric shrinkage and/or porosity of the casting. The casting shown in Fig. 4 is from a mold which had a multiplicity of spaced cavities I3 communicating with spaced parts of the mold cavity.

may be termed its forward end. 'I'he opening 2| is in the nature of a cylinder opening and is preferably cylindrical in transverse crossl section. 'I'he opening 2| is closed at its inner end by an end wall 2 Ia of the body.

Means is provided for mounting or supporting the body 20 in the cavity I3. g In Fig. 2 this means comprises an integral stem 22 extending from the rear end of the body 20 and adapted to be set or partially embedded in the sand of the mold I0. The stem 22 is not only effective in supporting the unit or body but valso acts to carry off excess gas developed in the unit. In Figs. 1 and 3 the supporting means for the body 2|) is in the form of a nail, spike, or rod 23 cast or embedded in the rear portion of the body 20 and projecting from the body to engage in the material of the mold III. There may be two or more stems 22 or rods 23 as practice requires.

In both of the arrangements just described the body 20 is supported so that it is bodily spaced a substantial distance from the walls of the cavity I3. The spacing of the body 20 from the cavity walls is suiiicient to allow a free flow of the molten metal around the body 20 and to insure that the body will extend into that portion of the metal which remains molten within the shell formed as a. result of the chilling of the.

occupies the outer portion of the opening 2| and Referring again to Fig. 1 the head or cavity I3 is sufliciently large to receive such a volume of molten metal that there will be a body of liquid or molten metal in the head cavity I3 communi-- eating with the molten metal in the mold cavity I2 when the crust or shell of metal solidifies in the mold .cavities through contact with the walls thereof. In other words, the capacity of the cavity I3 is such that the metal will not quickly chill in it to become a solid mass before the volumetric shrinkage occurs in the mold cavity I2. The shape of the cavity I3 may be varied as conditions require and the cavity I3 may extend in any selected or required direction from the mold cavity.' It should be observed that the cavity I3 may be much smaller than the heads employed where gravity and yatmospheric pressure are depended upon tomake up for volumetric shrinkage.

The pressureunit I4 is a feature of the invention. We will refer rst to the unit 'I4 shown in Figs. 1 and 3, it being understood that this description is applicable generally to the other units that may be employed.

The unit I4 includes a body 20 adapted to be supported withinthe head or cavity I3. 'I'he body 20 is preferably formed of refractory material such as baked fire clay, baked core sand, or other suitable material. If desired the surfaces of the body 20 or at least its external surfaces may be glazed or otherwise made impervious to moisture.

The body 20 in its simple form is an elongate element proportioned to be received in the cavity- I3 with substantial clearance. A central longitudinal opening 2| enters the body 2li from what when in the initial or normal position may have its outer end fiush with the end of the body 20. To facilitate handling a suitable seal or retaining means may be employed to hold the plunger in the opening 2|. It is preferred to make the 'plunger 24 of substantial length and to form it of the same material as the body 20, although it may, if desired, be formed of metal or other suit able material. y

The unit I4 further includes a .charge 25 in the opening 2| behind the plunger 24, the charge being of a material that is adapted to increase a substantial amount in volume when subjected to high temperatures, such as accompany rnolding metals and like materials. Vermiculite may be used as the active ingredient for the charge 25. With this material it is desirable to provide an igniting agent. This agent may be sawdust or other suitable material which will burn when heated and which will facilitate proper action of the vermiculite. The action of the charge is to force the plunger outwardly gradually and under a sustained pressure for a substantial period. When the charge is proportioned about as shown in Figs. 2 and 3 and is mad-e up of about twothirds by volume of sawdust and about one-third by volume of ground vermiculite it will act under heat from molten iron so the plunger is forced forward a considerable distance under a sustained pressure. The vermiculite may be ground to the size of coarse sand. The proportions given are by no means critical, they are given only as an example. Wide variations may occur in practice. Further, the size and action of the charge may be varied considerably by varying not only the Aproportions of the materials named but also the particular materials used in the charge.

When molten metal enters the cavity I3 and ilows around the body 20 the heat is transmitted through the walls of the body 20 and the charge 25 is activated by the increased temperature to create the sustained pressure for driving the the desired manner.

5 plunger 24 outwardly into the molten metal in the cavity I3. causing pressure on the molten metal in the mold cavity. The thickness of the body and the heat conductivity of the material fused in making the body 20 are balanced with the `charge 25 so that the heat from the molten metal reaches the charge and causes 'it to act in In practice these factors may be varied considerably depending upon the action desired and the heat of the material being poured.

In employing the apparatus of the invention and in carrying out the method the mold sections I and II may be made up in the lusual way to have the mold cavity I2, the head or cavity I3 and the pouring gate Il. In making up the mold the body 2U is arranged in the cavity I3 `to be in spaced relation to the several walls of the cavity. As above described the body 20 may be supported in the cavity I3 by the stem 22 or the rod 23 as the case may be, tovbe spaced a substantial distance from the several walls of the cavity I3. When the mold has been made up and assembled the mold may be poured in the usual way.

The molten metal is poured into the gate II to flow into the mold cavity I2 and the cavity I3, When the molten metal enters the cavity I3 it flows around the body 2U to immerse or substantially immerse the same and the walls of the body 20 transmit the heat of the molten metal to the charge 25. This high temperature activates the charge 25 and the material of the charge generates pressure behind the plunger 24.which pressure forces the plunger outwardly.

After the pouring operation the gate I1 may be chilled or "frozen or otherwise sealed off so that the molten metal is confined entirely within the cavities I2 and I3. The plunger 24 forced outwardly into the molten metal in the cavity I3 ,compensates for or feeds the volumetric shrinkage which accompanies the solidification of the metal in the mold cavity I2. In this connection it is important to note that the plunger 24 is positively forced outwardly from the body 2n by a sustained, gradually increasing pressure developed by the charge 25. The body 20 is spaced a suilicient distance from the walls of the cavity I3 so that the plunger 24 moves into the molten body of metal which is an extension of the molten body of metal in the mold cavity I2, and the crust or shell of metal which solidifes as a result of chilling when it engages the walls of the cavities does not aiTect the operation of the plunger. The plunger 24 forced outwardly into the mass of molten -metal effectively feeds the volumetric v shrinkage to insure the production of a sound,

dense casting having aminimum of internal stresses.

As described above, there may be two or more of the units I4 arranged in as many heads or cavities I3 communicating with those portions of the mold cavity I2 where the volumetric shrinkage is likely to be excessive. Fig. 4 illustrates three units applied to a single casting.

Fig. 5 illustrates the manner in which a unit I4 may be employed in the pouring gate 30 of a mold to feed the volumetricv shrinkage of the metal in the mold cavity |23. Whenthe pressure unit or units I4 are employed in this Way the need for a separate head cavity I3 is completely eliminated. The gate opening becomes the cavity to receive the pressure unit. We use the term cavity to refer either to a` separate or specially formed cavity or to a cavity formed by a gate or other such portion of the mold.

In Fig. 5 the mold is provided with the required mold cavity and the pouring gate 30 communie cates with the cavity to `conduct the molten :metal thereto. The gate 30 or a portion of the gate is suillciently large in diameter to receive the pressure unit I4 with adequate clearance. The mold is made up in the usual Way and when ready the molten metal is introduced through the gate 30. A sufficient quantity of metal is poured to completely occupy the mold cavity I2a and to extend a considerable distance upwardly into the gate 30. Following the pouring of the mold the pressure unit I4 is entered into the molten metal standing in the gate 30 and is suitably supported in a position where it is immersed or partially immersed in the molten metal. In the drawings we have shown rods or wires 3l connected with the stem 32 or rod 23 and engaged on or in the upper mold section to sustain the pressure unit I4 in the gate.

When the unit I4 has been arranged in place the upper end of the gate 33 is closed by said or other material. The unit I4 functions substantially as described above. The charge 25% generates pressure behind the plunger 24 to force the plunger Aoutwardly into the molten mass of metal in the gate 30 which is in direct communication with the molten metal in the mold cavity |23. The plunger 24 forced into the molten metal under a sustained pressure feeds or compen-v sates for the volumetric shrinkage accompanying the solidifying of the metal in the mold cavity, providing for a sound casting that is dense and practically devoid of internal stresses.

In most cases it will be desirable to apply one' or more pressure units to the exterior of a cast` ing as desribed above. In some instances it may be desirable to embed one or more units directly inside a casting to be permanently embedded in` the finished casting. In this case the unit or units, as the case may be,` may be suspended in the mold cavity by wires, stems, or any suitable means.

It is to be understood that the pressure units may be varied Widely in size. shape and even in mechanical form, the essential feature being that the charge is responsive to the heat of the matcrial being molded so that expansion occurs, oilsetting the shrinkage of material in the mold. By properly balancing the unit or number of units to the casting very satisfactory results can be obtained.

It is also to be understood that the charge 25 can be varied not only as to its composition or material, so long as it has the desired action in response to the heat involved, but it may also be varied as to quantity to get the desired action. If a charge is used` which generates gas in an -appreciable quantity it may be desirable in practice to use a sealing medium between the plunger and body. If the plunger fits fairly close in the body there will be little tendency to escape between the plunger and body,

Having described only typical preferred forms of apparatus of our invention, we do not wish to be limited or restricted to the specific details herein set forth. but wish to reserve to ourselves any variations or modifications that may appear to those skilled in the art or fall within the scope of the following claims.

Having described our invention, we claim:

1. In combination with a mold having a casting cavity and a second cavity communicating therewith for the reception of the material to be cast,

heat conducted through the body from said material. and a part projected from the body by the charge and into the material to compensate for volumetric shrinkage of the material in the casting cavity.

2. In combination with a mold having a casting cavity and a second cavity communicating therewith for the reception of the material to be cast, means for feeding the shrinkage of the solidifying material in the casting cavity including a unit in the second cavity adapted to be immersed in the material received therein and operable to increase in volume when immersed in the material.

3. In combination with a mold having a. casting cavity and a secondv cavity communicating there-- with for the reception of the material to be cast, means for compensating for the shrinkage oi the solidifying material in the casting cavity including a pressure unit in said second cavity operable by heat from the material being cast to exert a pressure on said material when immersed by the material received in said second cavity.

4. Apparatus of the character described including a mold having a casting cavity and a second cavity in communication with the mold cavity adapted to receive a. body of the molten metal which is to be cast in the casting cavity, and means for compensating for the shrinkage of the metal in the casting cavity accompanying the solidifying of the metal, said means comprising a body in said second cavity having an opening, a plunger in said body opening movable into the molten metal, and a charge in said opening behind fthe plunger responsive to the heat from said molten metal to generate pressure for moving the plunger into the molten metal..

5. Means for use in a mold to compensate for the shrinkage of the molten material in a mold,

` said means including a body adapted to be arranged in the mold to be immersed in said material, the body having a cylinder opening, a plunger in said opening adapted to be projected therefrom, and a charge in said opening behind the plunger operable when heated as a result of said immersion of the body to generate pressure for projecting the plunger into said material.

6. Means for use in a mold to compensate for the shrinkage of the molten metal in a. mold, said means including a body adapted to be arranged in the mold to be immersed in the molten metal, the body having a cylinder opening, a plunger in said opening adapted to. be projected therefrom, and a charge in said opening behind the plunger operable when heated as a result of said immersion of the body to generate pressure for projecting the plunger into said material, said charge containing vermiculite.

7. Means for use in a mold to compensate for the shrinkage of the molten material in a mold, said means including a body adapted to be arranged in the mold, means on the body for supporting the body in the mold in a position to be immersed in said material, the body having a cylinder opening, a plunger in said opening adapted to be projected therefrom, and a charge vin said opening behind the plunger operable when heated as a result of said immersion of the body to generate pressure for projecting the plunger into said material.

8. Means for use in a mold to compensate for the shrinkage o! the molten metal in a mold, said means including a body adapted to be arranged in the mold. a stem on the body adapted.

to be engaged in the mold to support the body in a podtion where it is adapted tobe immersed in the molten metal, the body having a cylinder opening, a plunger in said opening adapted to be projected therefrom, and a charge in said opening behind the plunger operable when heated as a result of said immersion of the body to generate pressure for projecting the plunger into said material, said charge containing vermiculite.

9. Means for use in a mold to compensate for ths shrinkage of the molten metal in a mold, said means including a body adapted to be arranged in the mold to be immersed in the molten metal, the body having a cylinder opening, a plunger in said opening adapted to be projected therefrom, and a charge in said opening behind the plunger operable when heated as a result of said immersion oi' the body to generate pressure for projecting the plunger into said material, said chargey containing vermiculite and sawdust.

10. Means for use in a mold to compensate for the shrinkage of the molten metal in a mold, said means including a body adapted to be arranged in the mold to be immersed in the molten metal, the body having a cylinder opening, a plunger in said opening adapted to be projected therefrom, and a charge in said opening behind the plunger operable when heated as a result of said immersion of the body to generate pressure for projecting the plunger into said material, said charge containing coarsely ground vermiculite.

11. Means for use in a mold to compensate for the shrinkage of the molten metal in a mold, said means including a body adapted to be arranged in the .mold to be immersed in the molten metal, the body having a cylinder opening, a plunger in said opening adapted to be projected therefrom, and a charge in said opening behind the plunger operable when heated as a result of said immersion or the body to generate pressure for projecting the plunger into said material, said charge containing coarsely ground vermiculite and material for aiding the action oi.' the vermiculite.

12. Means for use in a mold to compensate for the shrinkage oi.' the molten metal in a mold, said means including a body adapted to be arranged in the mold to be immersed in the molten metal, the body having a cylinder opening, a plunger in said opening adapted to be projected therefrom, and a charge in said opening behind the plunger operable when heated as a result of said immersion of the body to generate pressure for projecting the plunger into said material, said charge containing coarsely ground vermiculite and sawdust.

13. Apparatus of the character described including a mold having a casting cavity and a second cavity in communication with the mold cavity adapted to receive a body of the molten metal which is to be cast in the casting cavity, and means for compensating for the shrinkage of the metal in the casting cavity accompanying the solidiiying of the metal, said means comprising a body in said second cavity having an opening, a plunger in said body opening movable into ithe molten metal, and vermiculite in said opening behind the plunger for generating pressure to force the plunger into the molten metal when subjected to the heat of said molten metal contacting the body.

14. Apparatus of the character described including a sand mold having -a casting cavity and a second cavity in communication with the mold cavity adapted to receive a body of the molten i the molten metal, and a part connecting the unit and the sand of the mold to carry off excess gas.

PHILLIP CAMPBELL. WILLIAM H. MAXWIELL.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name V Date 62,113 Cazalat 1---- Feb. 19, 1867 117,249 Bessemer July :25, 1871 315,741 Henderson Apr. 14, 1885 316,544 Henderson Apr. V28, 1885 1,227,175 Morris May 22, 1917 1,272,062 Lake July 9, 1918 2,181,157 Smith Nov. :28, 1939 2,205,327 Williams June 18, 1940 2,253,822 Sundback Aug. 26, 1941 2,295,227 Mackett Sept. 8, 1942 OTHER REFERENCES Page 253, Transactions of the American Foundrymens Association, voi. 50, 1942. 

